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SubjectRe: [PATCH v2 0/6] PPIN (Protected Processor Inventory Number) updates
On Mon, Jan 31, 2022 at 01:31:49PM +0100, Borislav Petkov wrote:
> On Fri, Jan 21, 2022 at 09:47:37AM -0800, Tony Luck wrote:
> > ...
>
> They look good so far on my PPIN-enabled AMD box.
>
> > 5) Add "ppin" to /sys/devices/system/cpu/cpu*/topology/ppin
> >
> > The big question for this part is whether there is a better
> > place to expose this value. I'm open to other suggestions.
>
> Yeah, I'm not sure about that either. I have
>
> $ grep -r . /sys/devices/system/cpu/cpu*/topology/ppin | cut -d: -f 2 | uniq -c
> 32 0xxxxx
>
> 32 times the same number.
>
> Wouldn't
>
> /sys/devices/system/node/
>
> be a better place?

Maybe.

> Even if those were logical nodes, it would still be less needless
> replication and that would be one more way for root to figure out which
> logical nodes belong to the same physical package... :-)

That would work for existing products. There are some cases where
a single package appears as mutiple nodes. But that's ok ... as you
say, one more clue to the topology.

I'm worried that some future thing might reverse that and have
a "package" id for each die in a multi-die package which still
appears as a single node. That would distort the meaning of "package",
so it isn't supposed to happen. But if it did, Linux would be stuck
just reporting one of the "package" ids.

-Tony

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